Means for safely servicing thermionic apparatus



May w, 1942. E, A E 2,283,729

MEANS FOR SAFELY SERVIC JING THERMIONIC APPARATUS Filed Oct. 21, 1941 2 Sheets-Sheet 1 INVENT OR. 50 n/A/m GGAGE ATTOR ND- May 1, 1942.

E. G. GAGE MEANS FOR SAFELY SERVICING THERMIONIC APPARATUS Filed 001:. 21. 1941 2 Sheets-Sheet 2 1N VENTOR. fawn/z DG-GAGE Panel May19, 1942 MEANS FOR SAFELY SERVICING THERMIONIC APPARATUS Edward G. Gage, Brooklyn, N. Y.', assignor of twothirds to Leon Ottinger, New York, N. Y.

Application October 21, 1941, Serial i io. 415,894

14 Claims.

The invention relates to the operation of thermionic apparatus requiring dangerously high potentials, for example, such apparatus as television and other cathode-ray tube apparatus, as

well as radio transmission and receiving apparatus, etc. In a copending application Serial #396,546 filed June 4, 1941, I have disclosed an arrangement whereby apparatus of this nature is safeguarded against dangerous anode currents to allow of access to the otherwise dangerous portions of the apparatus when necessary, as for servicing the apparatus. Such safeguarding is effected, generally; by including a high resistance between the source of dangerous voltage.

and the device to be operated, the resistance being located so close to said source that all parts of the circuit likely to be contacted by the human body lie beyond said resistance, the magnitude of the resistance being of such value that upon contact of the body with any exposed part of the circuit, the voltage falls to a harmless value. In this particular embodiment, provision has been further made to operate the thermionic apparatus at a subnormal value of the current suiiicient, however, to provide the necessary indications for the adjustments required without experiencing possible discomfort from undue, though safe, currents.

The present invention relates more especially to apparatus wherein the operating voltage and current employed are not normally of a safe value.

It has for an object to permit the operation of such apparatus with current which is not normally safeguarded, contact with dangerous portions of the apparatus being prevented by suitably enclosing the source of dangerous voltage and dangerous current, as well as the thermionic device and the anode circuit thereof in a suitable casing.

A further object of the invention is to provide the casing with means whereby access may be had to such normally dangerous portions, but only after the same have automatically been properly safeguarded.

Another object of the invention is to provide the casing with a movable closure member which cooperates with means adapted to render the power-reducing means normally ineffective but whereby the same is rendered fully effective when the movable member opens the casing to provide access to the circuit portions which then have thereby been made safe.

Still another object of the invention is to house suitably certain portions of the anode circuits in embodiments where those portions remain dangerous.

The invention has for an object also to provide for an operative circuit and apparatus. admitting of the use of current values greatly in excess of those possible with the arrangement set .forth in the aforesaid pending application Serial No. 396,546.

In carrying out the invention, there is provided a transformer as a source of power supply, the same having means for reducing to a safe value the anode current, as by introducing impedance or magnetic leakage, or by permanently including in series with one of its windings a resistance of sufficient magnitude to decrease the value of the anode current flow to a subnormal though operative value, means being provided to normally reduce its efiective value or entirely short-circuit said resistance. The resistance is selected to be of such magnitude that if contact be had with any exposed part of the circuit beyond such resistance, the current is reduced to a safe value. A casing encloses the transformer, thermionic device, and connecting conductors, and the casing is provided with a movable closure member normally preventing access to the different apparatus. In this condition, a member cooperating with the movable closure member provides for rendering inefiective the power-reducing means with respect to the transformer output so that the full value of current is available for operation of the thermionic device. However, when access is to be had to the interior of the casing, the power-reducing means is immediately made effective through withdrawal of the cooperating member by operation of the closure member thereon, thereby rendering the exposed portions of the circuit safe though furnishing adequate current for test purposes.

The nature of the invention,- however, will best be understood when described in connection with the accompanying drawings, in which:

Fig. 1 is a more or less diagrammatic view illustrating a thermionic device operating normally at a dangerous voltage and dangerous current but combined with means for reducing auto:

matically this current to a subnormal operative and safe value when it is desired to service the apparatus.

Fig. 2 is a similar view illustrating a modification as Well as a different type of thermionic device.

Figs. 3 to 5 are more or less diagrammatic views illustrating modifications in the power-reducing means cooperating with the power supply transformer.

Referring to the drawings, more particularly Fig. 1 thereof, there is disclosed the circuit connections for operating a thermionic device or oscillator ID in producing and transmitting electromagnetic oscillations. The oscillator is connected to the transmitting antenna. ii in the usual manner and may comprise a thermionic radio-frequency tube having the plate l filament l3, and grid l4, said grid and filament being energized from a transformer l5 while the plate is energized from a transformer l6 and at a dangerously high potential and.current.

The former circuit from transformer 15 constitutes no serious source of danger, whereas the plate or anode circuit in the ordinary assembly of such apparatus is quite unsafe, and it is the purpose of the present invention to make it possible to contact the same, as during servicing thereof, without serious results.

As in the ordinary practice, the entire apparatus is suitably enclosed, for example, in a casing 20 of insulating material or of metal, said casing, however, being provided with a movable member, for example, in hinging the back M of the casing to the bottom thereof so that'access may be had to the interior of the casing 20 when required. Bodily contact with portions of the circult operating at dangerous voltages and currents will thus be prevented; and when it becomes necessary to have access to the interior, provision is made through the action of said movable member 2i to reduce'automatically the anode current flowing to the thermionic device to an extent that it shall no longer be unsafe in case of accidental contact therewith. This safe and temporarily subnormal value of the current will, however, be suiilcient to operate the apparatus to afford, for example. pilot" indications.

As indicated, this is accomplished by the provision of a resistance or other current-reducing means 25 which is permanently included in series with vone of the windings, for example, the primary 25 of the transformer l6 whose secondary aflords a source of dangerously high potential and dangerous current and is connected to the plate I2. This resistance is of such high magnitude as to decrease the value of the anode current flow to the thermionic device to a subnormal but operative value and also suchthat, upon the establishing of a closed circuit, as in the v 1 case --of contact between the anode circuit and the human body, the'current in such closed circuit will be reduced-by the said resistance to .a

-- safe value.

It is understood that this resistance 25 will be runyeneotive-ooiy when it isdesired tohave aocess to theinteriorof-casing 20; and to this end furtherprovision ismade to reduce the'efiective value of said resistance whentheclosure mem ber 2| is applied to'the casing to close the latter. Forexample, a short-circuiting means embodying a contact piece 30 is provided to bridge a circuit 3| about resistance 25, thus normally contact piece it follows the same outwardly under the action of spring 33 and opens the shortcircuiting connection across the resistance 25, This places the latter in series with the primary winding 26 of transformer It to reduce the current in the secondary or anode circuit therefrom to a subnormal and safe though operative value which, however, is of suiilcient magnitude to energize the antenna H for test or service purposes and a may be indicated on instruments 34 and 35 included in the antenna circuit and anode circuits, respectively. The reduction of the current is preferably to such an extent as to make servicing of the apparatus not objectionable when bodily contacting exposed portions of the circuit.

Similarly, a protective resistance 35 is arranged to be introduced in circuit with the condenser 31 of the anode circuit through a contact piece 38 movable with an extension of rod 32. The condenser and its protective resistance are preferably enclosed in a housing 39.

Upon completion of the servicing of the device or other operations thereon, back 2| is returned to its normal location, illustrated by the full lines, to close the casing; and the apparatus is then in condition for normal operation since rod 32 has thereby been moved inwardly to bring the contact piece 30 in position to bridge the circuit 3i, eliminating substantially the effect of the resistance 25 and thus restoring the optimum current fiow.

In the embodiment illustrated in Fig. 2, a cathode-ray tube 40 having the screen 4| is located at the opening 42 of a casing 43 for housing the entire tube and network so that access may not be had directly thereto. However, a movable back 44 is provided, being hinged to the bottom 45 of the casing as in the previously described embodiment so that, when required, access may be had to the interior of the casing 43.

The two anodes 46 and 41 of this cathode-ray tube are energized generally at high and dangervous voltages and similarly a dangerous current, the one anode 45 being energized fromthe secondary winding 50 of a transformer 5i and the anode 41 from the secondary winding 52 of a transformer 53. In series with the energizing,

circuits to the respective anodes 46 and 41 are included respectively permanently located resistances 55 and-56 of the required magnitude to reduceth'e current flow intheir respective cir- --cir'cuits toa'sa'fe value, as herelnbefore more fully .set forth.

- sistances 59 and 50 of relatively. high magnitude toieaknfi acharge when theanode currents are reduced; and the condenser 53 has included in series therewith a further and protective resistancefii. 'This latter-resistance and themete'ctive'resistance 56 for transforme'r'52 andthe. protective resistance 55 for transformer 5l, are

arranged to be temporarily included inthe respective anode circuits in a manner similar to that described in connection with the embodiment shown in Fig. 1,

For example, through the operation of the movable back 44, bridging elements 62, 63, and 54 carried by a spring-urged rod 65, whose one end contacts the said back, are moved to include the normally short-circuited resistances and to reduce thereby the current in the corresponding anode circuits to a safe value.

It is preferred to enclose these resistances 55 and 56 with their transformers in suitable housings B6 and 61 to insure against contact with portions of a circuit between a secondary and the corresponding protective resistance. Similarly, the condenser, protective resistance BI is enclosed in a housing 68, together with its condenser and the bridging element for the said protective resistance; and the actuating rod portions for controlling all of the said resistance pass through suitable openings provided in these housings.

It is understood, of course, that the anode current in these circuits will be of a high order of magnitude and therefore dangerous when the main casing is closed, but because of the protective housing which is customarily of metal and grounded, it is impossible to make bodily contact with any of these dangerous circuits.

Other power-reducing means as associated with a transformer may be similarly actuated from the closure member of a casing to reduce the required extent to the anode current, Thus, reference being had to Fig. 3, there is introduced into the circuit of the primary winding 10 of a power supply transformer II an adjustable impedance member comprising the helix l2 and core 13, one of which elements is movable relatively to the other, for example the core I3. Movement of this core axially of the helix is obtained through a rod 14, similar to the rods 32 and 65 of the previously described embodiment, said rod at its one end being attached to the corresponding end of the core and at its other spring-urged toward and contacting the closure member I5 of enclosing casing 16 to partake of the movement of the closure member when access is to be had to the interior of said casing.

Or, as indicated in the, embodiment shown in Figs. 4- and 5, the power reduction may be accomplished by adjusting the degree of magnetic leakage. In the former embodiment, this is efiected by interrupting as at 80 the core 8| of transformer 82 and completing normally the magnetic circuit by means of a movable core section 83. This in turn is carried by one end of a rod 85 whose opposite end is spring-urged toward and contacts the movable closure member 85 of enclosing casing 86.

As indicated in Fig. 5,'the core 90 of transformer 9! is substantially continuous and within the field of the same there is movable a leakage element 92 reciprocable through one of the legs of the core by means of a rod 93 attached thereto and passing through the opposite leg. This rod, similarly to those of the hereinbefore described embodiments, moves With the movable closure number 94 to effect a power reduction, this being provided when the leakage element 92 assumes the position shown in broken lines.

I claim:

1. The combination with an electrical power supply including a transformer having core, primary, and secondary elements affording a source said transformer, power-reducing power-reducing means ineffective when the closure member is applied to the casing to close the latter and to render said power-reducing means efi'ective only when the closure member is moved to permit access to the interior of the casing.

2.'The combination with an electrical power supply including a transformer having a core and a primary and a secondary winding thereon aifording a source of dangerously high potential and dangerous current, a thermionic device having a cathode and an anode connected to the secondary winding of said transformer, associated visual indicating means, and power-reducing means cooperating with the primary winding of the transformer to reduce the anode current from the secondary winding to a safe value operative to afford visual indications at said indicating means; of a casing enclosing said transformer, power-reducing means, and thermionic device, the casing including a closure member therefor, and means cooperating with the cloure member to render the power-reducing means ineffective when the closure member is applied to the casing to close the latter and to render said power-reducing means effective only when the closure member is moved to permit access to the interior of the casing.

3. The combination'with an electrical power supply including a transformer having a core and a primary and a secondary winding thereon aiiording a source of dangerously high potential and dangerous current, a thermionic device having a cathode and an anode connected to the reducing means effective only when the closure member is moved to permit access to the interior of thecasing.

4. The combination with an electrical power supply including a transformer having a [core and a primary and a secondary winding thereon affording a source of dangerously high potential and dangerous current, a thermionic device having a cathode and an anode connected to the secondary winding of said transformer, associated visual indicating means, and current-reducing means included in circuit with the primary winding of the transformer to reduce the anode current from the secondary winding to a safe value operative to afford visual indications at said indicating means; of a casing enclosing said transformer, current-reducing means, and thermionic device, the casing including a closure member therefor, and means cooperating with the closure member to render the current-reducing means ineifective when the closure member is appliedto the casing to close the latter and to render said current-reducing means effective only when the closure member is moved to permit access to the interior of the casing.

5. The combination with an electrical power supply including a transformer having a core and a primary and a secondary winding thereon affording a source of dangerously high potential and dangerous current, a thermionic device having a cathode and an anode connected to the secondary winding of said transformer, associated visual indicating means, and resistance permanently included in series with one of the transformer windings, said resistance being of such high magnitude as to decrease the value of the anode current flow to the thermionic device to a safe value operative to afford visual indications at said indicating means and, upon establishing a closed circuit through exposed parts and the human body, the current in such closed circuit is reduced by the said resistance to a safe value; of a casing enclosing said transformer, resistance, and thermionic device, the casing including a movable closure member therefor, and

means cooperating with the closure member to reduce the effective value of said resistance when the closure member is applied to the casing to close the latter and to render said resistance fully effective only when the closure member is moved to permit access to the interior of the casing.

6. The combination with an electrical power supply including a transformer having a core and a primary and a secondary winding thereon affording a source of dangerously 'high potential and dangerous current, a thermionic device having a cathode and an anode connected to the secondary winding of said transformer, associated visual indicating means, and resistance permanently included in series with one of the transformer windings, all exposed parts of a circuit lying between said resistance and the said thermionic device, said resistance being of such high magnitude as to decrease the value of the anode current flow to the thermionic device to a safe value operative to afford visual indications at said indicating means and, upon establishing a closed circuit through said exposed parts and the human body, the current in such closed circuit is reduced by the said resistance to a safe value; of a casing enclosing said transformer, resistance, and thermionic device, the casing including a movable closure member therefor, and means cooperating with the closure member to reduce the effective value of said resistance when the closure member is applied to the casing to close the latter and to render said resistance fully effective only when the closure member is moved to permit access to the interior of the casing.

7. The combination with an electrical power supply including a transformer having a core and a primary and a secondary winding thereon affording a source of dangerously high potential and dangerous current, a thermionic device having a cathode and an anode connected to the secondary winding of said transformer, associated visual indicating means, and resistance permanently included in series with one of the transformer windings, the resistance being of such high magnitude as to decrease the value of the anode current flow to the thermionic device to a safe value operative to afford visual indications at said indicating means and, upon establishing a closed circuit through exposed parts and the human body, the current in such closed circuit is reduced by the said resistance to a safe value; of a casing enclosing said transformer, resistance, and thermionic device, the casing including a movable closure member therefor, and means cooperating with the closure member to shortcircuit said resistance when the closure member is applied to the casing to close the latter and to render said resistance fully effective only when the closure member is moved to permit access to the interior of the casing.

8. The combination with an electrical power supply including a transformer having a core and a primary and a secondary winding thereon affording a source of dangerously high potential and dangerous current, a thermionic device having a cathode and an anode connected to the secondary winding of said transformer, asso-- ciated visual indicating means, and a resistance permanently included in series with the secondary winding of said transformer, all exposed parts 'of a circuit lying between said resistance and the said thermionic device, said resistance being of such high magnitude as to decrease the value of the anode current flow to the thermionic device to a safe value operative to aflord visual indications at said indicating means and, upon establishing a closed circuit through said exposed parts and the human body, the current in such closed circuit is reduced by the said resistance to a safe value; of a casing enclosing said transformer, resistance, and thermionic device, the casing including a movable closure member therefor, and means cooperating with the closure member to reduce the effective value of said resistance when the closure member is applied to the casing to close the latter and to render said resistance fully effective only when the closure member is moved to permit access to the interior of the casing.

9. The combination with an electrical power supply including a transformer having a core and a primary and a secondary winding thereon affording a source of dangerously high potential and dangerous current, a thermionic device having a cathode and an anode connected to the secondary winding of said transformer, associated visual indicating means, and a resistance permanently included in series with the primary winding of said transformer, all exposed parts of a circuit lying between said resistance and the said thermionic device, said resistance being of such highmagnitude as to decrease the value of the anode current flow to the thermionic device to a safe value operative to afford visual indications at said indicating means and, upon establishing a closed circuit through said exposed parts and the human body, the current in such closed circuit is reduced by the said resistance to a safe value; of a casing enclosing said transformer, resistance, and thermionic device, the casing including a movable closure member therefor, and means cooperating with the closure member to reduce the effective value of said resistance when the closure member is applied to the casing to close the latter and to render said resistance fully effective only when the closure member is moved to permit access to the interior of the casing.

10. The combination with an electrical power supply including a transformer having a core and a primary and a secondary winding thereon affording a source of dangerously high potential and dangerous current, a thermionic device having a cathode and an anode connected to the secondary winding of said transformer, associated visual indicating means, and a resistance permanently included in series with the secondary winding of said transformer, all exposed parts of a circuit lying between said resistance and the said thermionic device, said resistance being of such high magnitude as to decrease thevalue of the anode current flow to the thermionic device to a safe value operative to afford visual indications at said indicating means and, upon to a safe value; of a casing enclosing said transformer, resistance, and thermionic device, the

casing including a movable closure member therefor, and means cooperating with the closure member to reduce the effective value of said resistance when the closure member is applied to the casing to close the latter and to render said resistance fully effective only when the closure member is moved to permit access to the interior of the casing, and a housing within the casing for enclosing the transformer, resistance, and cooperating means.

11. The combination with an electrical power supply including a transformer having a core a and a primary and a secondary winding thereon affording a source of dangerously high potential and dangerous current, a thermionic device having a cathode and an anode connected to the secondary winding of said transformer and a rectifier and a condenser included in circuit therewith,

' associated visual indicating means, together with a series resistance permanently included in series with the secondary winding of said tranformer, and a further resistance included in series with the condenser, all exposed parts of a circuit lying between the said resistances and the thermionic device and the resistances being of such high magnitude as to decrease thevalueof the anode current flow to the thermionic device to a safe value operative to afford visual indications at said indicating means and, upon establishing a closed circuit through said exposed parts and the human body, the current in such closed cirapplied to the casing to close the latter and to l render said resistances fully efiective'only when the closure member is moved to permit access to the interior of the casing, and a housing within the casing for enclosing the transformer, firstnamed resistance, and cooperating means.

12. In apparatus according to claim 11: the

provision of a housing also for the further resistance and condenser, and cooperating means for the further resistance.

13. The combination with an electricalpower supply including a transformer having a core and a primary and a secondary winding thereon affording a source of dangerously high potential and dangerous current, a thermionic device having a cathode and an anode connected to the secondary winding of said transformer, associ-' ated visual indicating means, and an impedance member permanently included in series with one of the transformer windings, the impedance thereof being of such high magnitude as to decreasethe value of the anode current flow to the thermionic device to a safe value operative to afford visual indications at said indicating means and, upon establishing a closed circuit through exposed parts and the human body, the current in such closed circuit is reduced by the impedance of said member to a safe value; of a casing enclosing said transform er, impedance member, and thermionic device, the casing including a movable closure member therefor, and means cooperating with the closure member to reduce the efiective value of said impedance when the closure member is applied to the casing to close the latter and to render said impedance fully effective only when the closure member is moved to permit access to the interior of the casing.

14. The combination with an electrical power supply including a transformer having a core with a primary and a secondary winding thereon afiording a source of dangerously high" potential and dangerous current, a thermionic device having a cathode and an anode connected to the secondary winding of said transformer, associated visual indicating means, and means to vary the. magnetic flux of the core of said transformer to an extent to decrease the value of the anode current flow to the thermionic device to a safe value operative to aflford visual indications at said indicating means and, upon establishing a current through exposed parts and the human body, the'currenti'n such closed circuit is reduced by magnetic leakage to a safe value: of a casing enclosing said transformer, the means to vary the magnetic flux, and the thermionic device, the casing including a movable closure member therefor, and mean cooperating with the closure member to reduce the effective value of the magnetic flux when the closure member is applied to the casing to close the latter and to render said flux-varying means fully effective to reduce power only when the closure member casing.

EDWARD G. GAGE. 

